Dry electrical discharge coating process on aluminum by using titanium powder compact electrode

This study examines the electrical discharge coating process by using Ti powder compact electrode in pure nitrogen gas (dry EDC) to modify the surface of Al alloy. The stable dry EDC process on Al Alloy are explored via optimizing the discharge current, pulse duration, and duty factor. Experimental results show that the material deposition rate (MDR) and composition of films are closely related to the appropriate setting of discharge parameters. Only with adequate electrical discharge energy, the pure titanium nitride (TiN) film can form on the surface of Al alloy. Excessive electrical discharge energy in the dry EDC process will trigger the self-propagating high-temperature synthesis (SHS) reaction of Ti powder compact electrode and nitrogen gas, which deteriorates the surface quality of the deposit. A coarser TiN film coexisted with weak second phase (Ti₂N) and minor aluminum nitride (AlN) under this condition. Meanwhile, it also contained a few voids in the film due to incomplete coverage and microcracks resulted from thermal expansion mismatch between TiN and the Al matrix.